Volkswagen's Two Diesel Plug-In Hybrid Concepts: Detroit Auto Show

At the Detroit Auto Show, Volkswagen showed not just one but two concepts with diesel plug-in hybrid powertrains.

VW not only unveiled its CrossBlue Concept for a mid-size seven-passenger crossover, it also showed the CrossCoupe Concept it had premiered last year at the Beijing Auto Show.

Each vehicle uses a diesel-electric powertrain, which in the CrossBlue is rated at 306 horsepower combined.

Together, the turbodiesel engine and electric motors together put out a whopping 516 lb-ft of torque when all four wheels are powered.

But one factor that seems to have escaped notice is that the CrossBlue's hybrid system uses a new dual-clutch direct shift gearbox (DSG) designed specifically for use with hybrid and plug-in hybrid powertrains, either with diesel or gasoline four-cylinder engines.

According to Oliver Schmidt, general manager of VW Group of America's engineering office in Auburn Hills, Michigan, the single-motor hybrid transmission is designed to minimize the length of a transversely mounted four-cylinder engine with hybrid system.

While not all details are public, the system maximizes the diameter of the electric motor--it has been shown with 40-kilowatt and 80-kilowatt motors--but minimize length by packaging the clutches inside the motor to the greatest extent possible.

The 190-hp 2.0-liter turbodiesel engine is a new engine family that will eventually spread through other Volkswagen models. In the CrossBlue, it's paired to a 40-kilowatt (54-hp) version of the electric motor that's sandwiched between the engine and the new DSG transmission.

The CrossBlue's 0-to-60-mph time is quoted at just 7.2 seconds, and VW says the plug-in hybrid powertrain's 9.8-kilowatt-hour lithium-ion battery in the center tunnel gives it up to 14 miles of all-electric range, using only the rear motor for propulsion.

To obtain all-wheel drive, rather than powering the rear wheels mechanically, the CrossBlue uses a 85-kW (114-hp) electric motor to provide torque on demand. That motor is essentially the same one as is used in the upcoming Volkswagen Golf E battery-electric car.

VW calls the electric rear drive system "a propshaft-by-wire." In its architecture, it's broadly similar to the system used in the all-wheel drive version of the Toyota Highlander Hybrid.

Running in hybrid mode, the company estimates the CrossBlue would be rated at 35 miles per gallon combined (33 mpg city, 37 mpg highway), as well 89 MPGe in electric mode.

In fact, the CrossBlue's default driving mode is to run as a hybrid. If the driver opts for electric-only running--using that rear motor--the top speed is cut to 75 mph.

Drivers can also instruct the car to charge the pack using the engine--where zero-emission driving is desired.

Volkswagen sees the superior range of the diesel plug-in hybrid powertrain as a selling point, noting that the CrossBlue's 18.5-gallon fuel tank gives it a highway range of 660 miles.

One other sport-utility feature on the CrossBlue is a power takeoff for users to plug in coolers, lights, a stereo, or other electrical equipment--making the car effectively an auxiliary generator.

It sits next to the standard charging port on the driver's side that lets the CrossBlue plug into a charging station. The diesel-fuel filler is on the other side of the concept car.